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DENVER - A Denver mom who posted family photos online said she was horrified to find strangers using them for deviant fantasies called "baby role playing" or "adoption role playing."

Participants take strangers' photos of children and use them to create fake profiles on Instagram, Twitter, and other social media sites -- then engage in scenarios that involve one user acting pretending to be a child, while another acts as the child's parent or caregiver.

Amber Kozak said she may never have realized a stranger was using photos of her infant daughter, Hazel, if they hadn't followed her account.

"I was just looking on Instagram, and somebody had started following me," she said. "So I clicked on their profile to look and see who it was, and I saw a picture of my daughter."

Kozak said the photo was familiar, but the rest of the profile was not.

"She was talking about how her name was Gracie and she was a kitty," Kozak said. "It was [Hazel's] Halloween picture."

Kozak immediately confronted the user, who explained why he or she had taken the photos.

"Because it was good for role-playing," Kozak told CALL7 Investigator Theresa Marchetta.

"What did you think when you heard that?" Marchetta asked.

"I was just like, 'What?! Role playing with my daughter's picture?'" Kozak said. "It disgusted me. I was like, 'For what? Like, why would you do that?' It seemed sick."

Kozak said she considers herself savvy about social media, but had never heard of it being used like this.

"They use, like, weird babytalk for babies that aren't even old enough to talk," she said. "I just opened, like, a huge door of all this, this stuff that was going on. And I was just dumbfounded."

Detective Mike Harris, who investigates child sexual predators for the Jefferson County District Attorney's office, said role playing presents a serious challenge for law enforcement officers, who often need evidence of a crime to help parents get photos removed. That can be more difficult to establish when the original posts were public.

"It's hard to undo," said Harris. "Because those pictures are now out there somewhere, and being used for whatever purpose."

Harris said many online "adoptions" become sexual, and even violent.

"There's so many things out there that, to a lot of us normal people, just turn our stomachs," he said. "But there is a world of fantasy out there that people utilize."

Harris said his best advice to parents -- is to prevent strangers from accessing their photos in the first place.

"Set those privacy settings," he said. "Watch where you post your pictures and who has access to them."